Resistance exercise prevents impaired homocysteine metabolism and hepatic redox capacity in Walker-256 tumor-bearing male Wistar rats

Abstract

Objective: The aim of this study was to investigate changes in homocysteine (Hcy) metabolism and redox balance in response to exercise treatment in a tumor-bearing rat model.

Methods: Male Wistar rats were exposed, or not, to a resistance exercise program 6 wk before inoculation with Walker-256 tumor cells or vehicle. After application, rats maintained their routine for 12 d and were then sacrificed for plasma and liver analyses.

Results: Impaired Hcy metabolism was evident after 12 d of tumor cell inoculation as demonstrated by significantly increased (P < 0.05) plasma total homocysteine (tHcy) concentration (53%) and decreased plasma cysteine, methionine, and vitamin B12 concentrations. Decreased hepatic cystathionine β-synthase (CBS) and betaine-homocysteine S-methyltransferase mRNA levels were found in tumor-bearing rats but not in controls. Tumor inoculation also decreased levels of liver reduced glutathione (GSH) and increased hepatic oxidative stress compared with non-tumor controls. However, resistance exercise prevented the tumor-impaired transsulfuration pathway as demonstrated by the decreased plasma tHcy, hepatic CBS expression, and increased GSH in tumor-exercised versus tumor-sedentary rats. Remarkably, all measures of liver oxidative stress were suppressed by exercise training. Tumor weight was unchanged between groups.

Conclusion: Resistance exercise prevented tHcy accumulation and liver oxidative damage caused by Walker-256 tumor cell inoculation; the modulatory effects of resistance exercise on Hcy metabolism appear to be at the level of transsulfuration pathway.

Keywords: Exercise; Homocysteine; Liver; Oxidative stress; Tumor; Walker-256.